"While his family were still hoping for an appeal and had no news from the case, the Islamic Republic unexpectedly executed him," tweeted opposition activist account 1500Tasvir - along with a heartbreaking video of Shekari’s family reacting to the news of the 23-year-old's execution, which took place Thursday.
Shekari had been accused of blocking Tehran’s Sattar Khan Street on 25 September and of using a machete to attack a member of the Basij Resistance Force, a volunteer paramilitary group loyal to the government. He was found guilty of 'moharebeh', or 'enmity against God'.
He appealed against the verdict, but it was upheld by the court on 20 November, according to state media.
His family had not been given any news about his case, according to reports.
Oslo-based group Iran Human Rights have criticised authorities' handling of his case, saying Shekari was "denied access to his lawyer throughout the interrogation phase [and] legal proceedings".
Nationwide protests that erupted across Iran after the death of 22-year-old Kurdish-Iranian woman Mahsa Amini on 16 September have posed one of the biggest challenges to the country's system of clerical rule since its establishment in 1979.
The government has responded with brutal force to the protests, killing, injuring and arresting hundreds of people. At least 475 people - including at least 68 children - have been killed since the protests began, according to rights group HRANA.
More than 18,000 people have been arrested, HRANA has said.
Rights groups fear that the Iranian government could carry out more executions in the coming months.